1. Field of the Invention
The invention relates to a method for the recognition of a command supplied to an interactive system by a user of the system, in which in one section of a program
(a) the system asks the user of the system a question in the form of a speech signal, PA0 (b) next, a command recognition unit is switched on for recognition of a command to be supplied to the system by the user, PA0 (c) depending on the result of the recognition procedure in step (b), and on the basis of a decision model, the system makes a choice of one reaction from a group of at least two possible reactions to the command, and PA0 (d) next, this reaction is then presented to the user by the system.
2. Description of the Related Art
The invention also relates to an interactive system for the implementation of the method.
An example of the method of the type mentioned in the preamble is shown in FIG. 1. The method could, for example, be implemented in an automatic ticket issuing machine for obtaining train or bus tickets, with the mutual transfer of information taking place by means of the spoken word. The method begins at block 10 and runs to block 11 in which step (a) is carried out, that is to say, the system asks the user/buyer the first question, for example:
question 1: "Do you want to buy a train ticket or a bus ticket?" In addition, step (b) is then carried out: the command recognition unit is switched on. After that, the user gives his first command in block 12 (or in other words: his first answer), for example:
command 1: "(I want) a train ticket".
The decision model is indicated with block 13. The decision model chosen is very simple. It can only select from two reactions. One reaction is that the program runs back via the circuit 14 and the block 15 to block 11. This path is chosen if the command recognition unit has not recognized the command which was given. In block 15 the system then gives, for example, the following information:
"Your command was not recognized. I shall repeat the question."
If a command is in fact recognized (and let us assume for a moment that the command has also been recognized correctly, namely the command that the user has also given--which need not necessarily be the case!) then the program runs to block 16, in which the next question is asked by the system, for example:
question 2: "What is your destination?" To which the user could, for example, answer in block 17:
command 2: "Amsterdam".
Next the decision procedure in block 13' again takes place, which can lead to the program running via the circuit 14' and the block 15'--in which the same information as in block 15 is given to the user, namely that the command has not been recognized--to block 16 for the repetition of the question. When a command is recognized the program runs to block 18 for the third question:
question 3: "What station do you want to go to?" Which in block 19 could be followed by:
command 3: "Amstel station". The fourth question might be:
question 4: "Do you want to travel first or second class?" To which the answer in block 21 is, for example:
command 4: "Second class".
The blocks 13" and 13'" again indicate the decision phases and 14" or 14'" and 15" or 15'", respectively, indicate the circuits that are gone through if no command is recognized.
In block 22 the system indicates the price of the ticket.
In block 23 the buyer pays, so that in block 24 he receives his ticket, after which the program stops in block 25.
In FIG. 1 the program sections 26, 26', 26", . . . etc. are indicated with the dashed lines. The program sections 26 and 26' have block 16 in common. The program sections 26' and 26" have block 18 in common, . . . etc.
It should be mentioned here that program sections may also contain larger units than the units 26, 26'. . . .
The method shown in FIG. 1 has a great advantage. If the recognition is correct in all sections of the program, then the user very quickly obtains a ticket. This is because the system asks a following question immediately after recognizing a command and does not first give further information to the user relating to the command which it has recognized.
The method shown in FIG. 1 also has a number of disadvantages. For instance, it may occasionally happen that the user discovers only when he or she arrives at program section 26'" that in an earlier section of the program the system has recognized a different command from the one he or she gave, so that the user is now in a completely different branch of the dialogue. For example, he/she wanted to buy a bus ticket and only found out in program section 26'" that he/she was in the dialogue for obtaining a train ticket.
Another disadvantage is that because of its simplicity the system is fairly rigid. A command is either accepted or it is not. In the latter case the question is always repeated, which can be very annoying.
Yet another disadvantage lies in the fact that in changing circumstances during the command recognition, particularly for example in those cases where the conversation between a user and the system takes place via the public telephone network--the transfer (path) from the mouth of the speaker/user to the input of the system changes in terms of time--the system cannot adjust its reactions to these changing circumstances.